Adding assets for the redesign

Blue icons are for main categories. Green icons are for use in the rest
of the page.
Merge pull request #10 from sanjeevdwivedi/master

Added Icon Design Files
# Updated header, footer and container layout styles in the default.html layout to look similar to the facebook developers page
Merge branch 'master' of git://github.com/facebook-csharp-sdk/facebook-csharp-sdk.github.com